Porting the EMPLOYEE database from Firebird 2.0 to MySQL 5.1 part 2

More on calculated columns, here is the create table statement for one of Firebird's Employee.fdb database:

CREATE TABLE SALARY_HISTORY (
EMP_NO EMPNO NOT NULL,
CHANGE_DATE DATE DEFAULT 'NOW' NOT NULL,
UPDATER_ID VARCHAR(20) NOT NULL,
OLD_SALARY SALARY NOT NULL,
PERCENT_CHANGE DOUBLE PRECISION DEFAULT 0 NOT NULL
CHECK (PERCENT_CHANGE BETWEEN -50 AND 50),

NEW_SALARY COMPUTED BY
(OLD_SALARY + OLD_SALARY * PERCENT_CHANGE / 100),

PRIMARY KEY (EMP_NO, CHANGE_DATE, UPDATER_ID),
FOREIGN KEY (EMP_NO) REFERENCES EMPLOYEE (EMP_NO));

I'd go for a trigger based implementation.

After this I'll look at implementing checks and foreign keys (color coding to highlight relevant code samples, I know it can be ugly ;-))